Method of coating articles with pyroxylin



March 29, 1932. w. c. HAMPTON METHOD OF COATING ARTICLES WITH PYROXYLINFilefld Oct. 28, 1929 Patented Mar. 29, 1932 UNITED S ATES- PATENTOFFICE wanna *c. more, or neuron, OHIO, assronoa '10 m cmwronn, monsoonarm cams! column, or narrow, 01:10, a coaroaa'rron or onto mo or coa'rmomirror-Es wrm rmxrnm ama filed October as, 192a. se-m1 no. 402,831

' This invention relates to a method of coat ing articles of metal, woodor other material with a covering of celluloid or of pyroxyhn applied ina liquid form and subsequently 5 cured thereon to afford a continuous,onepiece, adherent covering of substantially uni-:.

highly polished surface.

While reference is made in. some prior 1 patents to proposedapplications of celluloid or pyroxylin as a coating material by dippingarticles in a body of the materialm liquid form, such suggestions havebeen prophetic only andthe necessary teaching for successful workin ofnitrocellulose materials in liquid form llas been entirely lacking.lGreat difficulty is encountered 1n con-. trolling the materialsubsequent to the dipping operation and in effecting a curing of thecoating which will leave the finished; surform thickness and possessinga smooth and face undistorted and unblemished; Many "unusual problemshave been presented in effecting a uniformly smooth, pohshedsurfacedeposit for which the hereinafter stated method affords 'a commerciallypractical solution.

The solvents employed in reducing .pyroxylin and celluloid to liquidform are highly volatile, evaporating rapidly and permitting thematerial -to .set quickly upon withdrawal from the dipping bath. Suchrapid evaporation produces a refrigerating effect, causing precipitationof moisture from the surrounding atmosphere upon the-coated surface. Ifsuch moisture condensation trickles in streams upon the newly coatedsurface, it produces streaks and discoloration as well as "distortiojnand a rough or, matte surface. If such condensation stands in the formof dew, ice crystals, or drops upon the freshly coated surface, itproduces a rough and pitted surface effect.v If the outer surface of thedeposit ispermitted to set too quickly, it forms an impenetrablefilmwhich prevents the escape of solvent from the inner strata and byun-uniform' shrinkage of such outer surface film upon the inner materialwhile yet in a soft condition, it induces and produces a crinkledsurface of intricate design. If the freshly coated body .vide a methodor process of is maintained at a moderate temperature suflicient toeffect rapid evaporation of the solvent before such surface film canform, the solvent is quite likelyvtofboil er vaporize within the depositof coating material, thus forming pimples and bubbles and causing thematerial to swell or balloon often assuming 'odd and grotesque shapes.From the experience of many such failures, the hereinafter method orprocess of successful treatment of articles by dipping in liquidpyroxylin or v celluloid has been evolved.

The object of'the present invention is to provide a comparativelysimple, economical, and commercially practical method for coveringvarious articles of wood, metal and other materials, such as steeringwheels for automobiles, door knobs, handles for cutlery, golf club headsand shafts, bathroom fixtures, toilet seats, and numerous other articlesof everyday commercial and household use with a covering of celluloid oryroxylin having a uniformly smooth surf cepossessing a natural highpolish or luster without the necessity of mechanical polishing orfinishing operation, and of increased durability and capable ofwithstanding hard usage and wear,'and which will provide a continuousone-piece covering without seams or oints,

completely sealing the enclosed body against entrance of moisture orattack by vapors or the like.

A further object of the invention is to provide an improved method orprocess of applying celluloid and pyroxylin in liquid form andcontrolling the resulting deposit to prevent watering from rapidevaporatiompitting or eggshell surface affect from dew or ice crystaldeposits -'of moisture condensation, pimpling and bubble formation asresult-of boiling or vaporization of the con-' tained solvent, andwrinkling or orange peel affect due to un-uniform shrinkage.

A further object of the invention is toprovide a method and process bywhich various articles may coated with celluloid or pyroxylin of variouscolors, giving to the articles pleasing and ornamental color 'afiects.

A further object of the invention is to proencasing cracking, chipping,crazing, and 'fracture.n A further object of the invention is to providea coating or covering material which, when applied to articlespossessinga degree of flexib ility oglqfsll iency su h as shafts or gblfclubgcanes, uinbrella hamd the like, willyield in unison with the coatedar ticle. a l a.

With the above primary and other incidental objects in view, as willmore fully appear. in the specification, the invention conslsts of thesteps and procedure, the apparatus and the method of operation or theirequivalents as hereinafter described and set forth in-the claims.

The accdmpanying drawing more or lessdiagrammatically illustrates theapparatus for carrying out the present process, and the a successivesteps and stages of the method.

In out. the present process any suitable solvent for pyroxylin or forcell uloid such as ether, alcohol, acetate, or thelike,

-'may be used. However, acetone is the best known and preferable solventfor this purpose.- The process consists of two major operations, to wit,first the preparation and applicationof a solution ofpyroxylin', andsecond the evaporation of the solvent while governing such evaporationby temperature control, and by preconditioning the air in which thesetting or curing of the material is effected.

Preparatory to the dipping or coating oper-v ation, the pyroxylin orcelluloid, asthe case may be, is thoroughly dissolved in a suitablesolvent until the material becomes a VISCOIIS heavy liq'uid. This mixingof the material and the initial coating or dipping operation are bestand preferably performed in a room of normaltemperature of approximatelyseventy degrees Fahrenheit. The viscous dip-V ping solution takesapproximately the same temperature or one somewhat iower, due to therefrigerating 'afiect of evaporation. In the accompanying drawing thepreparation anddipping room is indicated as 1 in which is located thetank or vat 2 containing the acetone solution of pyroxylin, theviscosity ofwhich is approximately of the consistency of a'cake'batt eror a thick molasses. This 1 liquid. proxylin, which asapproximatelyseventy degrees Fahrenheit is sufliciently viscous -to a slow flowingliquid, will become solidi liquid menace fied into a plastic havingconsiderable resistance to movement at lower temperature.

" The article to be coated, whether it be an automobile steering wheel,a golf club shaft or head, a door knob, a toilet seat or other articles,is dipped rather slowly into this viscous to prevent carrying airbubbles into the hquid, and: is then slowly withdrawn. The dippedarticle'is held momentarily over the tank or vat '2 to allow the excessmaterial to drain from the article. Because of the rapid evaporation,this drainage period must be quite short, varying from a few seconds toordinalfly lot more than a minute since theevaporationbf'tlreiclvenifoccurs quite rapidly with deleterious affect.The drip is sev-v ered or cut, and'the article inverted to allow theremaining surplus material to flow reversely over the article andredistribute itself.

' The coated article is slowly revolved, preferably about an axisintersecting the article or closely adjacent thereto, so thatdisplacement of the fiuid material by centrifugal influence isminimized. By this operation the liquid material is evenly distributedover the surface of the article. Whilecontinuing the rotation, the,article is immediately trans ferred to a refrigerating room of very muchlower temperature. V

In practice, articles coated with terial at a temperature ofapproximately seventy degrees Fahrenheit are transferred to a curingroom wherein a temperature of liquid maapproximately fifteen to twentydegrees below zero is maintained. This temperature change quitenaturally causes a great increase in the viscosity of the coatingmaterial and gives it the required set, whereby it is. not inclined tochange itsshape orv position. In the curing operation, advantage istaken of two physical conditions, i. e., the.

lowering of the temperature causes a lowering of the vapor tension,consequently theatmosphere can contain less water vapor'at the lowertemperaturethan at a high temperature, and advantage is taken also ofthe latent heat of evaporation. The rotation of the article ispreferably continued during the curing or' drying operation ;within thecold room. The acetone or other solvent employed is much less volatilein the cold room,

consequently the solvent escapesmore slowly from the deposited materialwithout expansion, thereb obviating the dangers of pimplmg or bu blingand ballooning by which the deposit would otherwise be distorted.

Even though the temperature of the room he maintained quite low, theevaporation of the solvent nevertheless. produces a refrigcratingefi'ect tending to lower the temperature of the coated article belowthat of the.

surrounding atmosphere, and thereby induce on the surface coatingcondensation of moisture in the form of ice crystals. ,This effect,

however, is counteracted by extracting the.

moisture fromthe air to a de ee well below the saturation point before te air comes in contact with the coated article. To this end the curingroom or cold room 3, as illustrated inthe drawing, is divided b apartition 4 into two compartments whic communicate with each other atthe top and bottom of the wall 4. In one of these compartments 5,

there are located refrigerating coils 6 by which the'air currentscirculating within the -;air after it has passed over the refrigerator 1coils 6. By raising the temperature of the curing air approximately fiveto ten degrees,

that is to say, from the temperature of minus twenty to minus fifteen orminus ten Fahrenheit, not only is danger of moisture condensation by therefrigerating effect of the evapcrating solvent removed, but the'capabilit of the air to absOrb the solvent vapors, whic qhave a greataflinity for moisture, is greatly increased.

v The chilling of the air within' the com partment.5 as it passes overthe coils 6 causes a downward'current of air whereas the air' passingfrom the bottom of the'comwpartmen't through the temperin unit 17, bywhich its temperature is raisef'is givena tendency to rise within thecuring room 3 outside the compartment 5 towhich theair returns throughthe space 9 above the partition 4 after passing over the coated articlesbein cured and absorbing therefrom the vaporized solvent. 'Thus the coldair in afcontinuous circulation;

descending in.the-compartment 5 and the slightly warmer air ascending inthe room 3 induces natural convectio'n'currents aflord' e slight warmingof the air, after it'has] been lowered to such temperature as to condense its entrained moisture, so increases its capacity to absorb andretain moisture that none of the small remaining amount ofmois-fl turein the air will'be condensed upon the surface of the work which, due tothe evaporating efiect of the solvent, is somewhat colder-than the aircirculating thereabout. The low temperature retards the'evaporation ofthe solvent, allowing sufficient time for the solvent to escape from thedeposited material without causing pimples orbubbles. The subjection ofthe coated-article to such. lowered temperature also enables a heavieror' deeper deposit to be retained upon the article than would otherwisebe possible. This coverings orcoatings of considerable thickness may beeffected by .a single dip- Y ing operation: To afiord coverings ofmaximum thickness, the dipping and curing operations may be repeatedseveral times.

By rotating the article not on} 'while' transferring it from the dippingtan or vat to the chill room but during the curing process, any tendencyof the material to change its position or shift upon the .article isobviated. As illustrated in the drawing, a hand trucklOcquipped with anair motor -11 supplied from a pressure reservoir '12 or other suitabledriving means maybe provided for rotating a series of removablevsupporting bars 13 having thereon studs or pins 14 upon which dippedarticles may be'temporarily mounted. In order that the article's mountedupon these supporting bars may be rotated about axes passing thruor'closely adjacent to thearticles, the bars 13 are provided withterminal cranks or oiisettrunnions 15 about which the supporting bars.and articles revolve. These supporting bars are removably engageable ina rack upon the hand truck 10 in which they are operativelyconnectedwith the driving motorfor slow rotation during transference from thedipping roomto the curing room. In the latter room they may be left uponthe truck 10 for continued rotation, or. may be transferred to asuitable rack in such room wherein the supporting bars are rotated bysuitabledriving means. I

At 16 there is shown a revoluble 'baror shaft for supporting annularcoated bodies such as toilet seats. In this case a straight bar 16extends through openings in a series of articles which are secured toarms 17 upon such bar. A toilet seat is alwaysprovided' with screw holesfor attachment of the hinge connection. These same holes may be utilizedfor attaching the seat to an arm 17 by which v it is' detachablyconnected with therotating a shaft or bar16. The present material'must'not be confused with lacquers made from cellulose base which arevariously used and applied in liquid form.

Such lacquers although derived from the same base to which are addedvarious gums and solvents diifer' widely from the present mate rial incharacter being brittle when dry, lacking' the tensile strength anddurability, and can be practically applied'only in thin coati'ngswhereas the present material can be ap plied to form a quite thickcasing or shell about the article which will be hard but tough andpractically unbreakable. "Although he commercial as pyroxylin, pyroxyle,or pyroxyline, otherwise known specifically as celluloid, is" the"preferable material, the invention is not material known I specificallylimited to this material but ineludes othernitrocellulose derivativeshaving the characteristics ofpyroxylin.

While the conditioning of the air in the curing room has been-describedas being cooled to an extreme low degree to precipitate'the moisture andthe temperature then raised to increase its vapor car g capacity beforeit reaches the article, suc an is not necessarily colder'than thesurface of thecoated article with which the circulating a-ir comes incontact. The evaporation of the solvent produces a refrigei atingefie'ct' which tends to lower the temperature of the surface below thatof the surrounding atmosphere even at the low temperature of the curingroom.

The various temperatures herein mentioned I are given for illustrativepurposes but with no intent to arbitrarily limitthis invention to suchstated'temperatures nor relative tfem-' perature ranges. It is to beunderstood that the temperature and'relative variations thereof may bevaried within reasonable limits to meet different conditions of use,differences in the material-composition and solvent em-- ployed, andresults desired.

- From the above description it will be ap parent that there is thusprovided a method of the character described possessing the'particularfeatures of advantage before enumerated as desirable, but'whichobviously is susceptible of modification in its steps, sequence, detailprocedure and arrangement of. apparatus without departing from theprinciple involved or sacrificing'any of its advantages.

While in order .to comply with thepatent statutes the invention has beendescribed in language more or less specific as tostructural features, itis to be',understood that the invention is'not limited to the specificdetails described, but that the means and method herein disclosedcomprise the preferred form of several modeszof putting theinvention'in'to effect, and the invention is, therefore, claimed in anyof its forms or modifications within the legitimateand valid scope ofthe appended claims.

I articles with material having a nitrocellulose H thus described-myinvention,"I claim: n Y i 1; The herein described method of coating Ibase or the like,=jc onsisting in reducing the s o'material' toasemi-liquid-form by-the,addi-.

tionof a solvent," dipping the article to be I; coated in the liquidmaterial at a temperature ofap roximateIyseVenty degrees Fahrenheit,draining the excess therefrom, severing. the-drip-and-meversing theposition of v the article to redistribute the surplus material andslowly-rotating thecoated article to main-- tain distribution,transferring the coated article into a; temperature of approximately Y"minus fifteen degrees Fahrenheit and subjecting the article to theaction of circulating air which has been previously chilled toapproximately minus twenty degrees Fahrenheit and then warmed toapproximatelyminus fifteen degrees Fahrenheit.

( 2. The herein described method of coatthe article into a semi-liquidsolution 0 I drying temperature Ofthe article.

ing articles with material havingpyroxylin characteristics or the like,consisting in dippin the article into a semi-liquid solution of t ematerial, drainin the excess material therefrom, subjecting t e coatedarticle to a temperature materially lower than that at which the articleis dipped to effect quick congealing and retard evaporator ofsolvent,and

drying the article at such low temperature in air from which moisturehas been extracted to a degree well below the dew point at suchtemperatu 1 t '3. The herein described method of coating articles withmaterial having pyroxylin characteristics or the like, consisting indippizlilg material, draining the exce s material therefrom, subjectingthe artic e to a lower degree of temperature than that at which it wasdipped-to eifect quick congealing, and drying the coated article in anarid atmosphere to prevent condensation of atmospheric moisture thereon.

4; The herein described method of coating atmosphere of lowertemperature than thatof the material in which the article. was

dipped whereby the solvent will be permitted to evaporate but slowly,and precipitation of atmospheric moisture will be obviated. 5. The,herein described method of coating articles with material having characteristics or the like, consisting 1n dipping the article into. asemi-liquidsolution of the material, drainin theexcess materialtherefrom, and subjecting the article while drying to a temperature,materially lower than that of the material in which it was di ped.

'6. The herein described metho of coating articles with material havingthe characteristics of pyroxylin or the like, includin dipping thearticle into a semi-liquid solution of the material at approximatelynormal atmos pheric temperature, and subjecting the dipped article whiledrying to a substantially zero Fahrenheit temperature substantially asand for the purpose-specified.

' 7. The herein described method of coating acteristics or thelike,jin'cluding dippingthe article to be coated in o a semi-fluidsolution of the materiahfdrainmgthe excess material therefrom,- anddrying the article at a temperature of approximately zero Fahrenheit, inpreconditioned air, the moisture content of articles withmaterialhavingpyroxylin charwhich is lowered belowthe; dew point atthe8. The herein describedmethod of coating artlcles with material ofpyroxylin characprevent bubbling and ing will be retarded until thesolvent has rial, drainingthe excess material therefrom, and drying thecoated article at a substantially zeroFahrenheit temperature whereby thesolvent will be maintained below boiling to pimpling and thedryevaporated to prevent wrinkling.

9. The herein described method of coating articles with material ofpyroxylin characteristics or the like, consisting in dipping the articlein a semi-liquid solution of the mate rial, draining the excessmaterial'therefrom, and drying the coated article at a temperatureapproximately seventy degrees Fahrenheit less than the temperature ofthe material at the time of dipping.

I 10. The herein described method of coating articles with pyroxylin orthe like, consisting in reducing the material to semi-liquid form by theaddition of a solvent, and maintained at approximately normalatmospheric-temperature, dipping the article in the liquid coatingmaterial, and subjecting the coated article to a' materially lowertempera ture by which the material is quickly 'congealedand loss ofsolvent retarded in an atmosphere from which excess moisture has thesolvent to prevent displacement, and subbeen extracted.

11. The herein described method of coating articles with material havinga nitrocellulose base, consisting in reducing the material to semiliquidform by the addition of a solvent, dipping the article therein'at amoderately high temperature, subjecting the dippedarticle to arefrigerating effect in an atmosphere wherein the moisture content ismaintained materially below the point of saturation.

12. The herein described method of coating articles with a materialhaving a nitrocellulose base, including reducing the material to asemi-liquid form by the addition of a solvent, dipping therein thearticle to be coated,

' chilling the coated article to congeal the coating material and retardevaporation of the solvent, and subjecting the article to a dry airtreatment'whereby condensation of moisture upon the coated surface willbe obviated.

13. The herein described method of coating articles with material havinga nitrocellulose base including reducing .the 'material 'to' asemi-liquid form by the addition of a solvent, dipping an article to becoatedtherein at a proximately normal room temperature, su jecting the'dipped article to a freezing temperature and simultaneously subjectingit to the action of air, the temperature of who has been previouslylowered to a lesser degree to effect precipitation of moisture and thenraised to a higher degree of temperature before reaching the coatedarticle.

' 14. The herein described method of coating articles with materialhaving a nitrocellulose base including reducing the material to asemi-liquid.form by the addition of a-solvent, i p n an jectingthe'dipped article to a substantially zero Fahrenheit temperature, andsimultaneously circulating thereaboutair from which moisture has beenextracted to a point below the dew point at the temperature of therefrigerating effect produced by evaporation of the solvent from thecoated article.

article to be coated therein, sub- 15'. The herein described method ofcoating articles with material having a nitrocellulose base includingreducing the material to a semi-liquid form by theadditi on of asolvent, dipping an article to be coated therein, subjecting the dippedarticle to a temperature of approximately seventy degrees (Fahrenheit)less than the temperature of the material in which it was dipped, andsimultaneously drying the dipped article in air from which moisture hasbeen extracted belowthe dew sequently removing the solvent from thecongealed coating material. v

17 The herein described method of coating articles with material havinga nitrocellulose base including reducing the material to a semi-liquidform by the addition of a solvent,

y the addition of a solvent,

effect congealing' dipping an article to be coated therein, con--gealing the coating material prior to remova of the solvent andcontrolling the subsequent evaporation of solvent whereby the solventwill escape slowly.

18. The herein described method of coating I articles with materialhaving a nitrocellulose base including reducing the material to asemi-liquid form by the addition of a solvent, dipping an article to becoated therein, setting the material prior to removal of the solvent,and subsequently evaporating the solvent therefromm an atmosphere whichhas that produced moisture and then rewarmed.

19. The herein described method of coating articles with material havinga nitrocellulose base including reducing the material to a semi-liquidform by the addition of a h solvent, dipping an article to be coatedtherein, congealing the material prior to the removal of the solvent andsubsequently removing the solvent.

20. The herein described method of coating articles with material havinga nitrocellulose been previously cooled to a degree lessthan by therefrigerating efl'ect of I the evaporating solvent to precipitate the 6I ea-Lace base including reducing the material to a semi-liquid form bythe addition of a solvent, dipping an articleto be coated therein, chillin the coating material upon the article to e ect congealment thereofand evaporating the solvent therefrom at a temperature less than that atwhich the coating material was applied. x v 21. The herein describedmethod of coat- 10 ing articles with material having a nitrocellulosebase including reducing the material to a semi-liquid form by theaddition of a sol vent, dipping an article to be coated therein,subjecting the coating upon-the article to a congealing treatment priorto the escape of the solvent and subsequently removing the solventsufiiciently slowly to prevent bubbling, pimples or blisters j in'anatmosphere from which moisture has been extracted to such degree as toavoid condensation at the surface temperature of the coated article.

In testimony whereof, I have hereunto set my hand this 19th day ofOctober, A. D. 1929.- 1 1 WILLIAM G. HAMPTON,

